A jury has convicted financier Allen Stanford on all but one of the charges he faced for allegedly bilking investors out of more than $7bn in one of the largest pyramid schemes in US history.

The Texan had pleaded not guilty to bilking 30,000 investors from more than 100 countries through bogus investments with Stanford International Bank.

Jurors on Tuesday found him guilty of 13 of 14 counts of fraud, conspiracy, moneylaundering and obstruction of justice which each carry maximum sentences of five to 20 years in jail.

Stanford, 61, has spent the past three years in jail after being deemed a flight risk shortly after his February 2009 arrest.

He remained stoic as the guilty verdicts were read, but his elderly mother, two adult daughters and a family friend dropped their heads into their hands in dismay. He will be sentenced at a later date.

His lawyers told reporters the verdict was a "disappointment" and vowed to appeal. Prosecution attorneys left the courtroom quickly, and were unavailable for comment.

Cassie Wilkinson, one of Stanford's victims, said Tuesday was a day she has long awaited.

'Unfit for trial'

"We were taken advantage of not just by Allen, but by a whole band of crooks," she said. "It's great to know there were 12 jurors who felt the same way."

The only non-guilty verdict was returned on Count 2, in which Stanford was charged with wire fraud for allegedly purchasing $9,000 Super Bowl tickets for Antiguan bank regulator, Leroy King.

The charge apparently presented some difficulties for the jury as they sent two questions to the judge on Monday in an attempt to clarify language in the testimony regarding that count and the law governing such gifts.

Badly beaten in a jailhouse brawl, Stanford was temporarily declared unfit for trial after he became addicted to painkillers while also on antidepressants.

He tried to have his case completely dismissed after claiming that the beating and drugs destroyed his memory, but a judge refused to believe him.

Defence attorneys at the trial tried to shift the blame to former chief financial officer James Davis, who he said perpetrated the entire fraud while Stanford naively placed his trust in his former college roommate.

They also insisted the bulk of investor money was lost due to mismanagement by court-appointed receivers after the US government seized the bank.

Prosecutors scoffed at the notion, and said Stanford funded his lavish lifestyle by siphoning off $2bn in investor deposits while pushing "bogus" certificates of deposits which promised artificially high returns based on "safe" investments.

Investigators could not find 92 per cent of the $8bn the bank said it had in assets and cash reserves.

As a dual citizen of the United States and the Caribbean country of Antigua and Barbuda, Stanford was known for his largesse, especially on the two paradise islands.

With a fortune of $2.2bn, Forbes Magazine ranked Stanford as the 605th richest person in the world in 2006.